1. Field of the Invention
The invention generally relates to an optical scanning arrangement for use in an optical scanner, for example a bar code reader.
2. Description of the Related Art
A typical optical scanner (for example a bar code reader) has a light source, preferably a laser light source, and means for directing the laser beam onto a symbol (for example a bar code symbol) to be read. On route to the symbol, the laser beam is generally directed onto, and reflected off, a light reflecting mirror of a scanning component. The scanning component causes oscillation of the mirror, so causing the laser beam repetitively to scan the symbol. Light reflected from the symbol is collected by the scanner and detected by a detector such as a photodiode. Decode circuitry and/or a microprocessor algorithm is provided to enable the reflected light to be decoded, thereby recovering the data which is represented by the bar code symbol.
In the type of scanner known as a two dimensional or 2D scanner, the scanning component causes the light beam to trace out a two dimensional path across the symbol to be read. The preferred pattern depends upon the nature of the symbols with which the scanner is to be used, but typical examples include Lissajous figures and raster patterns.
Two dimensional scanning patterns are generally produced by mounting the mirror on the scanning component in such a way as to permit it to oscillate in two perpendicular directions. Conventionally, separate drive mechanisms were required to produce oscillation in the x direction and in the y direction, but more recently scanning components have been devised which can provide the required two dimensional motion using only a single magnetic coil. Examples are shown in U.S. Pat. Nos. 5,168,149 and 5,280,165, both of which are assigned to the assignee of the current invention, and both of which are hereby incorporated by reference.